Apparatus for gaseous treatment of materials



Nov. 9, 1965 M. D. JEPSON 3,216,129

APPARATUS FOR GASEOUS TREATMENT OF MATERIALS Filed Feb. 15, 1962 2 Sheets-Sheet 1 INVEN 10R:

Mic/me 1. Dams JEPSoN ATTORNEYS:

Nov. 9, 1965 D, JEPSON 3,216,129

APPARATUS FOR GASEOUS TREATMENT OF MATERIALS Filed Feb. 15, 1962 2 Sheets-Sheet 2 7 3 0 *{EXP X FIG. 4

IN vENToR:

M lcHAE 1. Den/ s JEPSon ATTORNEYS: MIQMM/ United States Patent Ofitice 3,216,129 Patented Nov, 9, 1965 3,216,129 APPARATUS FOR GASEOUS TREATMENT OF MATERIALS Michael Denis Jepson, Ilkley, England, assignor to The Spooner Dryer & Engineering Co. Limited, llkley,

England Filed Feb. 15, 1962, Ser. No. 173,427 6 Claims. (Cl. 34-156) The present invention relates to the treatment of material and more particularly to apparatus for thermally treating sheet material in continuous lengths wherein both sides of the material are subjected to impingement by streams of heated gaseous medium without any external support, such as a conveyor, being provided for the material, at least in the region of such treatment and wherein the spent gaseous medium after impingement flows lateral of the material.

In the already proposed apparatus of the above described kind an attempt is made to control the position of the material being treated by appropriately choosing the size and relative dispositions of nozzles from which the heated gaseous medium is projected. Such apparatus have not always proved satisfactory especially when attempts have been made to increase the velocity of streams of gaseous medium so as to increase the rate of heat transfer. Although the pressure exerted on the web by the streams of gaseous medium projected through the nozzles is substantially higher than the static pressure of the gaseous medium, the area of the material upon which this higher pressure acts is very small compared with the remaining area of the web which is subjected substantially only to the static pressure. The total force exerted on the material by the streams of heated gaseous medium projected theretowards may therefore be actually much less than the forces exerted on the material by the static pressure.

The present invention envisages controlling the position of the material being treated not by the streams of gaseous medium projected towards the two sides of the material so much as by controlling the static pressure at the two sides of the material.

In previously proposed apparatus, as in the apparatus of the invention, the nozzles are mounted in at least one pair of opposed pressure chambers. The gaseous medium directed from the nozzles is discharged substantially uniformly over the two sides of the material. However there is an increase in the amount of spent gaseous medium flowing between each side of the material and the adjoining pressure chamber transversely of the material towards the edges of the material. Usually in the previously proposed apparatus the space available between the pressure chambers and the material permitting such spent gaseous medium to flow away is of substantially constant cross section so that in order to get the gaseous medium away from the material the velocity of the transversely flowing spent gaseous medium must be increased towards the edges of the material. To obtain this increase in velocity there must be at each side of the material a greater static pressure in the regions of the centre of the material than in the regions of the edges of the material. Moreover should the material become displaced from its normal path closer towards one pressure chamber, especially the edges of the material, then the velocity of the spent gaseous medium flowing away between the material and that pressure chamber must be still further increased due to the reduction in the flow cross section and consequently the static pressure at the central region of the material at that side further increase thus tending to blow the central region of the material towards the other pressure chamber. Thus any displacement of the material from its normal path may lead to further displacement thereof and consequent instability in the position of the'material.

According to the present invention any decrease in the static pressure from the central region of the material to its edge regions is substantially avoided.

The invention is further described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic transverse cross section of apparatus for thermally treating material in sheet form constructed according to the present invention,

FIG. 2 is a detailed diagrammatic perspective view of parts of opposed pressure chambers of the apparatus of FIG. 1,

FIG. 3 is a detail section on the line IIIIII of FIG. 1.

FIG. 4 is a graph serving to illustrate the theory behind the present invention, and

FIG. 5 is a view similar to FIG. 2 of a modified pressure chamber construction.

Referring first to FIGS. 1, 2 and 3, a continuous sheet of material 10, such as paper, is fed between opposed pressure chambers 11, 12. Front pressure chamber walls 13 and 14 which face one another are provided with openings 15 for the projection of heated air towards the material 10. The pressure chambers 11, 12 are supplied with heated air from supply chambers 16, 17 by axial flow fans 18, 19 driven by motors 20, 21 respectively. Spent air flowing transversely of the material 10 collects in an outer casing 22 from whence it finds its way back to the supply chambers through heaters 23, 24, such as finned steam pipes. The supply chambers 16, 17 are defined between the rear pressure chamber walls 25, 26 and the upper and lower walls 27, 28 of the casing 22. The heated air is thereby circulated along a substantially enclosed endless path. A proportion of the spent air can be withdrawn through an outlet 29 whilst make-up air may be supplied through inlets 30, 31 arranged close to some of the heaters 23, 24.

As can be seen from FIGS. 2 and 3 the openings 15 are arranged in rows transversely of the material whilst curved channel-like pieces 35 are attached to the front walls 13 and 14 so as to present to the material being treated facings of a particular curved shape. The shape of these facings is chosen so as to substantially avoid any decrease in static pressure of the spent air flowing transversely of the material 10 in directions away from the central regions of the material as will be described hereinafter with reference to FIG. 4.

In the graph of FIG. 4 the theoretical cross sectional area A available to the spent gaseous medium flowing transversely of the material is plotted against distance x measured from the centre of the material.

Let Q and v denote respectively the rate of flow (measured in volume per unit time) and the velocity of the gaseous medium through the area A and let p and p denote respectively the static pressure and the density of such gaseous medium.

Consider now the energy content of an elemental volume A by 6x of the stream: The rate of addition to this volume of work and kinetic energy from the main stream 1=PQ+- pQ The rate of addition to this volume of work from the added stream 6Q The rate of removal from this volume of work and kinetic energy in the main and added streams assuming the density p remains constant.

3 If it is assumed that all the kinetic energy of the streams of gaseous medium flowing through the nozzles is dissipated.

1+ 2= 3 glVlIlg 1 Q 'FP Q -idx If the static pressure p is to remain constant giving 2 2 1 z@ vQ v dz 0 Equation 1 Also Q=Av Equation 2 If the gaseous medium is directed evenly over the material Q=ax where a is a constant. Putting this in Equations 1 and 2 and solving:

where c is another constant.

Equation 3 is the equation of the shape of the facings of the pressure chambers shown in FIGS. 1 to 3. Theoretically the pressure chamber facings should touch one another at the centre but in practice it is necessary to part the pressure chambers slightly as shown so as to allow free passage for the material 10. Thus the practical form of the apparatus does not quite conform to Equation 3 but experimental apparatus constructed with the pressure chamber arrangement of FIG. 2 has proved itself capable of supporting 40 inches wide Wetted thin paper strip (of 20 gm. dry weight per sq. m.) on air without undue fluttering of the paper at an air pressure in the pressure chambers of /2 to 1 /2 inch water gauge.

If a non-uniform distribution of the air directed on to the material can be employed then the facings can each be made in two straight portions conforming to the Equation A=bx where b is a constant so simplifyingthe construction of the apparatus. Putting this in Equations 1 and 2 and solving:

Q=cx

Thus the rate of direction of gaseous medium on to the material per unit of transverse width is which is a maximum at the centre of the material and decreases towards its sides.

In the experimental apparatus referred to above there was some fluttering of the paper towards its edges and it is believed that this may be due to the break away of the boundary layer of air from the surfaces of the paper towards its edges.

The arcuate shape of the pressure chamber facings leads to a considerable divergence towards the ends of the passage formed between the pressure chamber facings and the material being treated for the exhausting gaseous medium. It is believed that the break away of the boundary layer can be avoided at least to a considerable extent if the maximum efiective divergence of the passages formed by the sheet material and the pressure chamber facings for the exhausting gaseous medium is made no more than 5 to 6 especially when treating very flimsy material. Some divergence is required sim ply to cope with the increasing quantities of the exhausting gaseous medium towards the edges of the material if the velocity of the exhausting gaseous medium is not to be progressively increased towards the edges of the material. The effective divergence is any divergence over and above that which is necessary to cope with the increasing quantities of gaseous medium towards the edges of the material or in other words it is that part of the Equation 3 Equation 4 divergence which actually effects a reduction in the spent gaseous medium velocity. Thus the actual divergence can be greater than 6.

The present invention may also be employed when treating materials which are moving in planes which are not horizontal. If the material is horizontal then it may be supported by maintaining a very slightly greater pressure in the lower pressure chamber than in the upper pressure chamber. However, when the material is moving vertically such material can be tensionless except for its own weight in which case the primary object is to blow the gaseous medium onto the two sides of the material without causing undue flapping and it can be seen that the principles of the present invention apply equally as much as when the material is horizontal.

In the apparatus illustrated in FIGS. 1 to 3 the nozzles in the front faces 13 and 14 of the pressure chambers are well spaced apart. As is well known the quantity of gaseous medium which it is necessary to blow on to the material becomes the greater the further are the nozzle openings from the material if a given rate of heat transfer is to be obtained. In order to increase the rate of heat transfer and in addition or alternatively to enable the rate of supply of heated gaseous medium to be reduced the nozzle openings can be arranged closer to one another as shown in the modified pressure chamber construction of FIG. 5. As can be seen in FIG. 5, the pressure chambers 41 and 42 have all their nozzle openings arranged on a level with the tops of the arcuate or curved facings so that in effect increasingly divergent channels are provided for the exhausting gaseous medium between pressure chamber protrusions 43, 44 in which the nozzle openings 45 are provided.

Although round holes are shown in the drawings as nozzle openings, slit like nozzles or any other shaped nozzles may be employed as desired.

In the drawings the facings are shown as false facings or separate parts secured to the front faces of the pressure chambers. In alternative embodiments the facings themselves may form the front boundaries to the pressure chambers.

The present invention may be employed for drying paper or textiles, for heat treating plastic coated paper or textiles, for heat treating coated or uncoated films of plast ic material, for solvent removal from impregnated or coated paper or textiles, and in fact for substantially any kind of heat treatment of flexible sheet material wherein it is desired to treat both sides of the material simultaneously without touching the surfaces of such materials.

It is desirable, as shown in the drawings, that the gaseous medium be recirculated along an endless path and so used over and over again in order to avoid excessive wastage of heat. If the heat treatment involves vaporisation, as the evaporation of water or a solvent, then it is desirable to remove a proportion of the gaseous medium being circulated and to supply fresh make-up gaseous medium to avoid saturation of the gaseous medium with the water or solvent. The supply of make-up gaseous medium may be omitted when the heat treatment involves no evaporation.

I claim:

1. In apparatus for thermally treating sheet material, such as paper, in continuous lengths wherein streams of gaseous medium are directed on to both sides of the material for the exchange of heat with the material and to provide guiding support for the material and wherein the spent gaseous medium flows laterally of the material: the combination comprising opposed pressure chambers, means for supplying gaseous medium to said pressure chambers, .front Walls on said pressure chambers facing one another, said front walls having a plurality of rows of openings for directing streams of gaseous medium towards sheet material between said pressure chambers, and arcuate facing means positioned between said rows of openings on said pressure chamber front walls, whereby the arcuate facing means in combination with said openings maintains the static pressure of spent gaseous medium flowing laterally of the sheet material after said directing at least as great at the lateral edges of the material as at the central region of the material.

2. In apparatus for thermally treating sheet material, such as paper, in continuous lengths wherein streams of gaesous medium are directed on to both sides of the material for the exchange of heat with the material and to provide guiding support for the material and wherein the spent gaseous medium flows laterally of the material: the combination comprising opposed pressure chambers, front walls on said pressure chambers facing one another, said front walls having a plurality of rows of openings for directing streams of gaseous medium towards sheet material between said pressure chambers, and arcuate facing means positioned between said rows of openings on said pressure chamber front walls, said openings being uniformly distributed over said pressure chamber front walls and said arcuate facing means being shaped so that the square of the cross sectional area between the arcuate facing means and a plane tangent to the arcuate facing means at the longitudinal centre thereof is proportional to the cube of the distance of said cross sectional area from said longitudinal centre.

3. In apparatus for thermally treating sheet material, such as paper, in continuous lengths wherein streams of gaseous medium are directed on to both sides of the material for the exchange of heat with the material and to provide guiding support for the material and wherein the spent gaseous medium fiows laterally of the material: the combination comprising opposed pressure chambers, front walls on said pressure chambers facing one another, said front walls having a plurality of rows of openings for directing streams of gaseous medium towards sheet material between the pressure chambers, and arcuate facing means positioned between said rows of openings on said pressure chamber front walls, said openings being dimensioned and distributed so that the quantity of gaseous medium in the streams of gaseous medium project therefrom per unit area of the arcuate facing means at any given distance from the longitudinal centre thereof is inversely proportional to the cube root of that distance and said arcuate facing means being shaped so that the cross sectional area between the arcuate facing means and a plane tangent to the arcuate facing means at the longitudinal centre thereof is directly proportional to the distance of said cross sectional area from said longitudinal centre,

4. The combination according to claim 1 wherein the maximum net effective lateral divergence of said arcuate facing means relative to said sheet material is not greater than about 5 to 6.

5. In apparatus for thermally treating sheet material, such as paper, in continuous lengths wherein streams of heated gaseous medium are directed on to both sides of the material for the exchange of heat with the material and to provide guiding support for the material and wherein the spent gaseous medium flows laterally of the material: the combination comprising opposed pressure chambers, front walls on said pressure chambers facing one another, said front walls having a plurality of rows of openings for directing streams of heated gaseous medium towards sheet material between said pressure chambers, a casing arranged about said pressure chambers for collecting spent gaseous medium which flows laterally of said material after being directed theretowards, fan means for withdrawing spent gaseous medium from within said casing and supplying it to said pressure chambers for recirculation, heating means for said gaseous medium being recirculated, and arcuate facing means positioned between said rows of openings on said pressure chamber front walls, whereby said arcuate facing means in combination with said openings maintains the static pressure of said laterally flowing spent gaseous medium at least as great at the lateral edges of the material as at the central region of the material.

6. The combination according to claim 1 wherein the rows of openings are arranged on a level with the tops of the arcuate facings.

References Cited by the Examiner UNITED STATES PATENTS 2,071,015 2/37 Andrews 34-23 2,848,820 8/58 Wallin et al. 34156 X 2,884,711 5/59 Parkes 34-156 3,048,383 8/62 Champlin 34l56 X 3,060,594 9/62 Meier-Windhorst 34156 FOREIGN PATENTS 709,741 5/31 France. 768,878 2/57 Great Britain.

WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFF, PERCY L. PATRICK,

Examiners. 

1. IN APPARATUS FOR THERMALLY TREATING SHEET MATERIAL, SUCH AS PAPER, IN CONTINUOUS LENGTHS WHEREIN STREAMS OF GASEOUS MEDIUM ARE DIRECTED ON TO BOTH SIDES OF THE MATERIAL FOR THE EXCHANGE OF HEAT WITH THE MATERIAL AND TO PROVIDE GUIDING SUPPORT FOR THE MATERIAL AND WHEREIN THE SPENT GASEOUS MEDIUM FLOWS LATERALLY OF THE MATERIAL: THE COMBINATION COMPRISING OPPOSED PRESSURE CHAMBERS, MEANS FOR SUPPLYING GASEOUS MEDIUM TO SAID PRESSURE CHAMBERS, FRONT WALLS ON SAID PRESSURE CHAMBERS FACING ONE ANOTHER, SAID FRONT WALLS HAVING A PLURALITY OF ROWS OF OPENINGS FOR DIRECTING STREAMS OF GASEOUS MEDIUM TOWARDS SHEET MATERIAL BETWEEN SAID PRESSURE CHAMBERS AND ARCUATE FACING MEANS POSITIONED BETWEEN SAID ROWS OF OPENINGS ON SAID PRESSURE CHAMBER FRONT WALLS, WHEREBY THE ARCUATE FACING MEANS IN COMBINATION WITH SAID OPENINGS MAINTAINS THE STATIC PRESSURE OF SPENT GASEOUS MEDIUM FLOWING LATERALLY OF THE SHEET MATERIAL AFTER SAID DIRECTING AT LEAST AS GREAT AT THE LATERAL EDGES OF THE MATERIAL AS AT THE CENTRAL REGION OF THE MATERIAL. 